• Journal of Soil and Groundwater Environment
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• v.25 no.2_spc
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• pp.1-15
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• 2020

Monitoring and assessing terminal electron accepting processes (TEAPs) are one of the most important steps to remediate contaminated sites via various in-situ techniques. TEAPs are a part of the microbial respiration reactions. Microorganisms gain energy from these reactions and reduces pollutants. Monitoring TEAPs enables us to predict degradability of contaminants and degradation rates. In many countries, TEAPs have been used for characterization of field sites and management of groundwater wells. For instance, US Environmental Protection Agency (EPA) provided strategies for groundwater quality and well management by applying TEAPs monitoring. Denmark has also constructed TEAPs map of local unit area to develop effective groundwater managing system, particularly to predict and assess nitrogen contamination. In case of Korea, although detailed soil survey and groundwater contamination assessment have been employed, site investigation guidelines using TEAPs have not been established yet. To better define TEAPs in subsurface environments, multiple indicators including ion concentrations, isotope compositions and contaminant degradation byproducts must be assessed. Furthermore, dissolved hydrogen concentrations are regarded as significant evidence of TEAPs occurring in subsurface environment. This review study introduces optimal sampling techniques of groundwater and dissolved hydrogen, and further discuss how to assess TEAPs in contaminated subsurface environments according to several contamination scenarios.

• Analytical Science and Technology
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• v.32 no.1
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• pp.17-23
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• 2019

Sources of NOx are both anthropogenic (e.g. fossil fuel combustion, vehicles, and other industrial processes) and natural (e.g. lightning, biogenic soil processes, and wildfires). The nitrogen stable isotope ratio of NOx has been proposed as an indicator for NOx source partitioning, which would help identify the contributions of various NOx sources. In this study, the ${\delta}^{15}N-NO_2$ values of vehicle emissions were measured in an urban region, to understand the sources and processes that influence the isotopic composition of NOx emissions. The Ogawa passive air sampler was used to determine the isotopic composition of $NO_2$(g). In urban tunnels, the observed $NO_2$ concentration and ${\delta}^{15}N-NO_2$ values averaged $3809{\pm}2656ppbv$ and $7.7{\pm}1.8$‰, respectively. The observed ${\delta}^{15}N-NO_2$ values are associated with slight regional variations in the vehicular $NO_2$ source. Both $NO_2$ concentration and ${\delta}^{15}N-NO_2$ values were significantly higher near the expressway ($965{\pm}125ppbv$ and $5.9{\pm}1.4$‰) than at 1.1 km from the expressway ($372{\pm}96ppbv$ and $-11.5{\pm}2.9$‰), indicating a high proportion of vehicle emissions. Ambient ${\delta}^{15}N-NO_2$ values were used in a binary mixing model to estimate the percentage of the ${\delta}^{15}N-NO_2$ value contributed by vehicular NOx emissions. The calculated percentage of the ${\delta}^{15}N-NO_2$ contribution by vehicles was significantly higher close to the highway, as observed for the $NO_2$ concentration and ${\delta}^{15}N-NO_2$.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.129-135
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• 2013

Japanese larch (Larix leptolepis) has been extensively planted in Korea as a reforestation species but their supply has been a major bottleneck due to sporadic natural seed production. In this study, stem girdling was applied to 32-year-old grafted Japanese larches, resulting in significantly enhanced seed production compared to the controls. Stem girdling induced about 4 times higher cone production than that of controls in the Japanese larch seed orchard. Time-dependent metabolic alterations after girdling were investigated by stable isotope ratio mass spectrometer, HPLC, and GC-MS analysis. In girdled trees, the contents of total nitrogen, sucrose, and total free amino acids were significantly higher than the non-girdled trees at the flowering differentiation season (from July to August). Moreover, the numbers of female strobilus per tree were positively correlated with the contents of both total nitrogen (r=0.765, p<0.01) and total amino acids (r=0.802, p<0.01) in the bark being collected at the flowering differentiation time (August 20). Interestingly, the levels of various individual amino acids at the flowering differentiation times, such as aspartic acid, glutamic acid, glycine, serine, and cysteine, were also significantly correlated (p<0.05) with the numbers of strobilus, suggesting that those amino acids might be involved in the induction of female strobilus formation of Japanese larches.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.30 no.5
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• pp.782-793
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• 1997

To study the physiological adaptation (shift-up) of phytoplankton under the simulated upwelling conditions, nitrate uptake capacity of Dunaliella tertiolecta batch culture was measured in the laboratory using the stable isotope $^{15}N-KNO_3$. Contrary to the expected, there was no significant relationship between the maximum $V_{NO3}$ (nitrogen specific nitrate uptake rate) and the initial nitrate concentration. However, there was a strong relationship between the maximum $\rho_{NO3}$ (nitrate transport rate) and the initial nitrate concentration of $<25\;{\mu}M$, which was also influenced by the physiological status of the culture. The increase in $V_{NO3}$ was mainly due to the increase in PON (particulate organic nitrogen) concentration and partly due to the increase in $V_{NO3}$. When the phytoplankton population was severely shifted-down, the physiological adaptation of nitrate uptake was significantly inhibited at high initial nitrate concentrations. The timing of the maximum $V_{NO3}$ or $\rho_{NO3}$ was related to the initial nitrate concentration. At higher initial nitrate concentrations, maxima in $V_{NO3}$ and $\rho_{NO3}$ occurred 1 or 2 days later than at lower nitrate concentrations. This relationship was the opposite to the prediction from the shift-up model of Zimmerman et al. (1987), The shift-up process is apparently controlled by an internal time sequence and the initial nitrate concentration, but the magnitude of $V_{NO3}$ was affected little by changes in nitrate concentration.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.43-52
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• 2010

The geochemical and nitrogen isotopic analyses for shallow groundwater of Ogcheon area were carried out to characterize the geochemical characteristics of the groundwater and to identify the source of nitrate. Groundwater shows a neutral pH to weakly alkalic condition with pH values ranging from 6.9 to 8.4. The average of EC, Eh and DO is $344.2\;{\mu}s/cm$, 195 mV, 4 mg/L, respectively. According to piper diagram, chemical composition of groundwater is dominantly characterized by Ca-$HCO_3$ type. On the other hand, groundwater type in the study area include Ca-Cl+$NO_3$ type that were highly influenced by agricultural activities. $NO_3$-N concentration of the collected samples(n=45) range from 12.4 to 34.2 mg/l. These data show that the $NO_3$-N concentration exceeds Korea Drinking Water Standard (10 mg/l). The $\delta^{15}N-NO_3$ values range from $2.7^{\circ}/_{\circ\circ}$ to $18.8^{\circ}/_{\circ\circ}$. The enrichments of heavy isotope in the groundwater indicate that major origin of nitrate pollution were associated with animal and human waste. Also the denitrification may have partly contributed as one of the sources of nitrogen.

• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.1
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• pp.1-6
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• 2005

With recent interest organic farming the use of legumes including vetch and clover to provide N to adjacent crops is increasing in Korea. In the present studies, we conducted a trial to investigate the effects of the application of N rate on nitrogen fixation and transfer from vetch to barley in mixed stands. The experiment was arranged in a randomized complete block design with three replications. Four different N rates(0, 75, 113 and 150/ha) was used and vetch+barley was broadcasted manually on 1.5 $\times$2 m plot in Oct. 2001. Half of urea and K$_{2}O, 200 Phosphate and 75 kg potash per ha were applied as basal dressing md half of N md 75 potash were used for topdressing to soil surface on MarctL 2002. The equivalent of 1kg ha$^{-1}$ at($^{15}$NH$_{4}$)$_{2}$SO$_{4}$ solution at 99.8 atom $\%$$^{15}$N excess was applied to the microplot in mid April. Forage was harvested from each plot at ground level and separated into barley and vetch. Total N content and It values of samples were determined using a continuous flow stable isotope ratio mass spectrometry(IsoPrime-EA. Micromass, UK.). The percentage of legume H fixed from atmospheric N2 were 95.0, 93.8, 94.4 and $84.8\%$ with increment of N levels. The percentage of N transfer from vetch to barley by N-difference method with increment of N fertilizer were from 58 to$49\%$ while 39 to $23\%$ in $^{15}$N-dilution method. The amount of transfer from vetch to barley were 87 to 68 kg/ ha with N level by N-difference moth여 and 58 to -56/ha with N application levels by $^{15}$N dilution method. The amount of nitrogen fixation per ha were from 150 kg / ha to 219 kg / ha by different method, but on the other side 49 to 105kg/ha by N$^{15}$-dilution.

• Korean Journal of Environmental Agriculture
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• v.14 no.1
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• pp.97-108
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• 1995

Nitrate concentration and ${\delta}^{15}N$ value in the groundwater in Miyakojima Island, Okinawa, were measured during 1992-1993. Water from the shallow and the deep wells at the ten separate sites were sampled. Mineral contents and natural nitrogen isotope abundance(${\delta}^{15}N$) were analyzed using a liquid chromatography and a mass spectrometry (Finnigan MAT 252). Except for waters which were directly influenced by sea water invasion, most of the groundwater showed small variations among their mineral contents and ${\delta}^{15}N$ values. The average nitrate nitrogen concentrations were $1.4{\sim}11.5mgL^{-1}$ and average ${\delta}^{15}N$ values were +4.3${\sim}$+9.7$%_o$. From the nitrate concentration and ${\delta}^{15}N$ value observed, the types of the groundwater could be categorized into four groups, such as high ${\delta}^{15}N$ and high nitrate, high ${\delta}^{15}N$ and medium nitrate, low ${\delta}^{15}N$ and medium nitrate, and low ${\delta}^{15}N$ and low nitrate, reflecting the main source of nitrate contamination, such as animal and domestic waste, animal waste and soil organic matter, soil organic matter and chemical fertilizer, and chemical fertilizer, respectively. It was discussed that the lowest ${\delta}^{15}N$ value was higher than the ${\delta}^{15}N$ value of the chemical fertilizers used in this island(-3.9${\sim}$-1.4$%_o$), then considerable amounts of nitrogen must be lost by ammonium evaporation or denitrification after fertilization.

• Korean Journal of Environmental Biology
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• v.30 no.3
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• pp.210-218
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• 2012

The morphological characteristics, carbon and nitrogen concentrations, stable isotope values and photosynthetic rates of Porphyra yezoensis were studied at the main purple lavers production areas on southwestern coast of Korea. The morphological characteristics of leaf length, leaf width and weight of Porphyra blades were between 11.6~16.3 (average 13.8) cm, 4.6~6.3 (average 5.4) cm, $1.1{\sim}2.6(average\;1.86)g\;DW\;m^{-2}$, respectively. Photosynthetic pigment of Chl a concentration of Porphyra blades was between $2.18{\sim}17.77(average\;9.65)mg\;DW\;Chl\;a\;m^{-2}$. Carbon and nitrogen concentrations of Porphyra blades was between $201{\sim}317(average\;240)mg\;DW\;g^{-1}$, $39.8{\sim}50.0(average\;43.5)mg\;DW\;g^{-1}$ and C/N ratio 5.0~6.7 (average 5.5). The range of average ${\delta}^{13}C$ and ${\delta}^{15}N$ values of Porphyra blades was between - 25.6 to - 24.0 (average - 24.7)‰ for ${\delta}^{13}C$, and 1.3 to 4.1 (average 2.1)‰ for ${\delta}^{15}N$. Photosynthetic characteristics of seaweeds measured by pulse amplitude modulation (PAM) fluorometry was used as an indicator of photosynthetic activity. We use Diving-PAM fluorometry to examine photosynthetic rates of the seaweeds Porphyra yezoensis at each station. Maximum quantum yield of Porphyra blades was between 0.46~0.55 (average 0.52), the variance of the effective PS II maximum quantum yield of the station was broadly similar. Maximum relative electron transport rate (rETRmax) of Porphyra blades was between $4.71{\sim}5.84(average\;5.33){\mu}mol\;electrons\;m^{-2}\;s^{-1}$, the changes of maximum relative electron transport rate (rETRmax) of Porphyra yezoensis were similar to those of PS II maximum quantum yield. Photosynthetic efficiency (${\alpha}$) was between 0.027~0.045 (average 0.036). Minimum saturating irradiance ($E_k$) range was $139{\sim}180(average\;156){\mu}mol\;photons\;m^{-2}\;s^{-1}$. Minimum saturating irradiance ($E_k$) made a difference by station within the area on southwestern coast. Carbon and nitrogen concentrations and photosynthetic rates of Porphyra blades production areas on southwestern coast were broadly similar. The photosynthetic characteristics showed low photosynthetic rates because the low maximum quantum yields and low maximum relative electron transport rate.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.31 no.2
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• pp.259-266
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• 1998

A study on the biological and chemical characteristics in the middle last Sea of Korea was carried out at 31 stations in October $11\~18$, 1995 on board the R/V Tam-Yang. The chlorophyll a concentration, new and regenerated production, and the vertical diffusion of nitrate from the thermocline structure were investigated. From the vertical distribution of chlorophyll a, subsurface maxima were observed near the thermorline at most stations including the frontal zone, except at the southern stations where the maximum chloropyll a concentration occurred at the surface, The nanophytoplankton was the most dominant fraction comprising $83.5\%$ of total phytoplankton cell numbers, but netphytoplankton were common at the southern stations where the dominant species were Rhizosolenia sp. Nitrogenous new production and regenerated productions were measured using the stable isotope $^{15}N$ nitrate and ammonia uptake method. The vertically integrated nitrogen production varied between 8.470 and $72.945\;mg\;N\;m^{-2}\;d^{-1}$. The f-ratio, which is the traction of new production from primary production, waried between 0.03 and 0.72, indicating that $3\%$ to $72\%$ of primary production was supported by the input of nutrients from below the euphotic zone and the rest are supported by ammonia recycled within the euphotic layer. This range of f-ratio encompasses from extremely oligotrophic to eutrophic area characteristics. The differences in productivity and f-ratio among stations were related to frontal structure and the bottom topography. The values were high near the frontal zone and low outside of it, and the station near Ulleng Island showed the highest f-ratio. Vertical diffusion coefficients were calculated from both the water column stability (Kz-1) of King and Devol's equation (1979) and new nitrogen requirement (Kz-2). The values of Kz-2 ($0.11\~0.55\;cm^2/s$) were relatively low compared to the values reported previously.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.7 no.2
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• pp.60-67
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• 2002

To determine whether nitrogen (N) uptake by phytoplankton below the euphotic zone in the Yellow Sea is considerable, we measured the uptake rates of nitrate and ammonium using $^{15}N$-labeled stable isotope $K^{15}NO_{3}$ and $^{15}NH_{4}Cl$, in May and November 1997 at total 10 stations. Depth-integrated uptake rates of nitrate and ammonium over the euphotic zone during this study ranged from 1.8 to 15.3 mg N $m^{-2}$ $d^{-1}$ and from 5.0 to 132.2 mg N $m^{-2}$ $d^{-1}$, respectively, and ammonium uptake predominated at 9 of 10 stations (1.9-19.4 fold). Depth-integrated uptake rates of nitrate and ammonium over the whole water column ranged from 2.9 to 22.0 mg N $m^{-2}$ $d^{-1}$ and from 15.7 to 175.5 mg N $m^{-2}$ $d^{-1}$, respectively. The significant proportion of whole water column N uptake was attributed to uptake by phytoplankton below the euphotic zone, ranging from 13.0 to 86.2% for nitrate and from 13.8 to 67.8% for ammonium, indicating that phytoplankton N uptake below the euphotic zone is at times considerable in the study area. The results suggest that when phytoplankton below the euphotic zone in the Yellow Sea are again entrained into the euphotic zone by a certain physical forcing such as turbulent mixing and the vertical movement of thermocline, these episodic events may significantly affect the material fluxes within the euphotic zone. Furthermore, the results suggest that a portion of regenerated production estimated from $^{15}N$-ammonium uptake should be included in new production estimates, which otherwise could be underestimated in the Yellow Sea.